Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$131.47	10.727%	$145.5728	$145.57	$145.55	$145.60
Purchase #2	$195.50	13.214%	$221.3334	$221.33	$221.35	$221.30
Purchase #3	$90.25	11.292%	$100.441	$100.44	$100.45	$100.40
Purchase #4	$82.65	10.414%	$91.2572	$91.26	$91.25	$91.30
Purchase #5	$213.53	7.458%	$229.4551	$229.46	$229.45	$229.50
Purchase #6	$28.92	10.360%	$31.9161	$31.92	$31.90	$31.90
Purchase #7	$208.62	3.848%	$216.6477	$216.65	$216.65	$216.60
7 purchase totals =	$950.94		$1,036.6233	$1,036.63	$1,036.60	$1,036.60